Corrections of the original CFPREV control in the LCC-HVDC links and analysis of its inherent plateau effect

The most effective approach to suppressing the first commutation failure (CF) of the LCC-HVDC link at fault inception is to advance firings of the inverter, and the commutation failure prevention (CFPREV) control is the most commonly used method in practical engineering. However, it is found in this letter that there exist a few serious defects in its original scheme, and thus targeted vital corrections have been made in the first place. Furthermore, an interesting phenomenon termed the plateau effect that an excessive advancement of firings will contrarily and inevitably lead to more commutation failures is also revealed and analyzed, and it turns out that for which the inherent commutation dents of the Graetz bridge should be mostly responsible, which bridges the knowledge gap and further enhances the cognition of the limitation of CFPREV control, and it may also conduce to the design of related control parameters. Simulation results then validate the imperative of those presented corrections and confirm the existence of the plateau effect.